diff --git a/lazarus/DBConnection.pas b/lazarus/DBConnection.pas
index acc9928..9197ebf 100644
--- a/lazarus/DBConnection.pas
+++ b/lazarus/DBConnection.pas
@@ -58,7 +58,7 @@   TDBConnection = class
     // updateInserts student object into database. Either updates an existing one or inserts a new one
     // parameter: student object
     // result: TRUE on success
-    function updateInsertStudent(student: TStudent): boolean;
+    function updateInsertStudent(var student: TStudent): boolean;
 
     // Deletes a student and destroys the object
     // parameter: student object
@@ -77,13 +77,13 @@   TDBConnection = class
     // Returns an array of all rentals with given student and book
     // parameter: student, book
     // result: array of rental objects
-    function getAllRentalsByBookAndStudent(student: TStudent;
-      book: TBook): ArrayOfRentals;
+    function getAllRentalsByBookAndStudent(var student: TStudent;
+      var book: TBook): ArrayOfRentals;
 
     // updateInserts rental object into database. Either updates an existing one or inserts a new one
     // parameter: rental object
     // result: TRUE on success
-    function updateInsertRental(rental: TRental): boolean;
+    function updateInsertRental(var rental: TRental): boolean;
 
     // Deletes a rental and destroys the object
     // parameter: rental object
@@ -111,7 +111,7 @@   TDBConnection = class
     // updateInserts book object into database. Either updates an existing one or inserts a new one
     // parameter: book object
     // result: TRUE on success
-    function updateInsertBook(book: TBook): boolean;
+    function updateInsertBook(var book: TBook): boolean;
 
     // Deletes a book and destroys the object
     // parameter: book object
@@ -126,16 +126,16 @@   TDBConnection = class
     // result: array of booktype objects
     function getBooktypes: ArrayOfBooktypes;
 
-    // updateInserts booktype object into database. Either updates an existing one or inserts a new one
-    // parameter: booktype object
-    // result: TRUE on success
-    function updateInsertBooktype(booktype: TBooktype): boolean;
-
     // Returns the Booktype of an ISBN Number
     // parameter: Isbn (String type)
     // result: TBooktype on success, NIL on failure
     function getBooktypeByIsbn(isbn: string): TBooktype;
 
+    // updateInserts booktype object into database. Either updates an existing one or inserts a new one
+    // parameter: booktype object
+    // result: TRUE on success
+    function updateInsertBooktype(var booktype: TBooktype): boolean;
+
     // Deletes a booktype and destroys the object
     // parameter: booktype object
     // result: TRUE on success
@@ -399,7 +399,7 @@ function TDBConnection.getStudentByLDAPUser(ldap_user: string): TStudent;
     Result := arr[0];
 end;
 
-function TDBConnection.updateInsertStudent(student: TStudent): boolean;
+function TDBConnection.updateInsertStudent(var student: TStudent): boolean;
 begin
   DBError := nil;
   SQLQuery.Close;
@@ -536,8 +536,8 @@ function TDBConnection.getRentals: ArrayOfRentals;
   setRentalFields(Result, False);
 end;
 
-function TDBConnection.getAllRentalsByBookAndStudent(student: TStudent;
-  book: TBook): ArrayOfRentals;
+function TDBConnection.getAllRentalsByBookAndStudent(var student: TStudent;
+  var book: TBook): ArrayOfRentals;
 begin
   DBError := nil;
   SQLQuery.Close;
@@ -565,7 +565,7 @@ function TDBConnection.getAllRentalsByBookAndStudent(student: TStudent;
   setRentalFields(Result, False);
 end;
 
-function TDBConnection.updateInsertRental(rental: TRental): boolean;
+function TDBConnection.updateInsertRental(var rental: TRental): boolean;
 begin
   DBError := nil;
   SQLQuery.Close;
@@ -760,7 +760,7 @@ function TDBConnection.getBookById(id: longint): TBook;
     Result := arr[0];
 end;
 
-function TDBConnection.updateInsertBook(book: TBook): boolean;
+function TDBConnection.updateInsertBook(var book: TBook): boolean;
 begin
   DBError := nil;
   SQLQuery.Close;
@@ -887,7 +887,7 @@ function TDBConnection.getBooktypes: ArrayOfBooktypes;
   setBooktypeFields(Result, False);
 end;
 
-function TDBConnection.updateInsertBooktype(booktype: TBooktype): boolean;
+function TDBConnection.updateInsertBooktype(var booktype: TBooktype): boolean;
 begin
   DBError := nil;
   SQLQuery.Close;